Apparatus for varying pressure roll nip force

ABSTRACT

An apparatus for varying nip pressure in a media feedpath including a feed roller and a pressure roller defining a feed nip there between includes a rotatable cam having a preselected eccentric path when rotated, a first pivotable linkage pivotally engaging the rotatable cam, a second pivotable linkage, a biasing member operably interconnecting the first and second pivotal linkages for providing a biasing force on the pressure roller. The pressure roller is rotatably connected to the second linkage opposite the biasing member, wherein rotation of the cam varies the biasing force provided by the biasing member on the pressure roller.

CROSS REFERENCES TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

REFERENCE TO SEQUENTIAL LISTING, ETC.

None.

BACKGROUND

1. Field of the Invention

The present invention relates generally to media feed mechanisms, and more particularly to a media feed mechanisms in printing and/or scanning mechanisms.

2. Description of the Related Art

All-in-one machines typically perform functions such as printing, scanning, copying, and faxing in either a stand alone fashion or in conjunction with a personal computer and define a growing market for peripheral devices. These devices eliminate clutter in a business or home office by combining the desirable functionality of various machines into a single unit, while maintaining an affordable cost. Various all-in-one machines currently in the marketplace use thermal inkjet technology as a means for printing received fax documents, original documents, and copied or scanned images or text. Thermal inkjet printing devices utilize consumable inkjet cartridges in fluid communication with a printhead to record text and images on a print media. The printhead typically moves on a carriage relative to the media path and a control system activates the printhead to selectively eject ink droplets onto the print media.

Scanners are used to scan a target image and create scanned image data which can be displayed on a computer monitor, used by a computer program, can be printed, or can be faxed, etc. Scanned data may be saved to memory or a magnetic or optical drive, or other fixed or removable memory device. Scanning devices may be packaged in a stand-alone housing or as part of the all-in-one device, as described herein, including a printing module to perform scanning as well as standard copying functions.

Scanners typically include a housing aperture defined by an edge wherein a platen is located. A target document is positioned on the platen for scanning of the text or image by a scanbar. Depending on the positioning of the scanbar relative to the platen, the platen may be transparent where the scanbar is beneath the platen or may be solid where the scanbar is above the platen. For a typical flatbed scanner, the scanbar will be below the platen, which will have a transparent section to allow for the scan operation.

The scanner may also include an automatic document feeder (ADF) to automatically and sequentially feed a plurality of documents to a scan module. The ADF typically comprises a feed tray and an input device which feeds a single sheet from the stack of media on the feed tray into the ADF media path. The single sheet of media passes the reading position where the media is illuminated and image data is created by the scanbar representing images on the media. The media then passes from the ADF to a stacking tray where the media remains until all of the media from the feed tray has been scanned and is removed from the stacking tray at the output side of the ADF.

In either printing or ADF scanning, a printing medium or original document is transported by a feeding mechanism. The transport mechanism includes at least a pressure roller and a feed roll or driving roll. The pressure roll or idler roll forces the media against the feed roll during ADF scanning or printing. When in contact with the feed roll, the media is advanced for printing or scanning before engaging an exit roll. Prior art devices place a constant and continuous bias on the pressure roller in order to maintain engagement of the pressure roller and feed roll.

For ease of description, the following is directed to a printing mechanism such as an ink-jet printing operation, however, one of ordinary skill in the art should understand that the problems associated with prior art transport mechanism may also be associated with ADF scanners. When the media trailing edge exits the nip between the feed roll and the pressure roll, the media is urged forward in a feed direction. This advancement of the media occurs because a downward force of the pressure roller causes a tangential force having a component in the direction of media feed. The media may advance some undesirable distance corresponding to the backlash of a gear train driving the feed roller. The result is that media may advance some distance greater than the intended amount. The problem worsens when thicker media is utilized. Due to the over-advancement of the media, the printhead is moved from its intended position relative to the medium resulting in ink droplets being deposited inconsistently and reduced print quality. For example, banding may occur which is undesirable. In the case of ADF scanning, the media jump can result in scanning quality defects.

Given the foregoing, it will be appreciated that an apparatus is needed which varies the force applied to media trailing edge moving through a feed nip of a printing or scanning feedpath to eliminate media jump.

SUMMARY OF THE INVENTION

The present invention inhibits media jump when media exits the nip between the pressure roll and the feed roll.

According to a first embodiment, an apparatus for varying nip pressure in a media feedpath including a feed roller and a pressure roller defining a feed nip therebetween, comprises a rotatable cam having a preselected eccentric path when rotated, a first pivotable linkage pivotally engaging the rotatable cam, a second pivotable linkage, a biasing member operably interconnecting the first and second pivotal linkages for providing a biasing force on the pressure roller. The pressure roller is rotatably connected to the second linkage opposite the biasing member, wherein rotation of the cam varies the biasing force provided by the biasing member on the pressure roller. The cam has an eccentric shape. A rotatable shaft is operably connected to the cam. The first linkage pivots about a first linkage pivot point as the cam rotates. The cam loads and unloads the biasing member connected to the first linkage and the second linkage as the cam is rotated. The pressure roller exerts greater force on the feed roll as the biasing member is loaded and exerts lesser force on the feed roll as the biasing member is unloaded. The pressure roller comprises a plurality of pressure rollers.

According to a second embodiment, a variable pressure roll linkage for media feedpath comprises an elastic member, a first linkage, a feed drive roller and a pressure roller defining a nip therebetween, a second linkage with the pressure roller operably connected to the second linkage with the first linkage connected to the second linkage by the elastic member, a cam moveable about a preselected profile engages the first linkage wherein movement of the cam loads and unloads the elastic member and causes translation of the pressure roller at the nip. The pressure roller is translatable toward and away from the feed drive roller. Rotation of the cam pivots the first linkage. The elastic member further comprises a spring. The application of tension to the elastic member increases force of the pressure roll toward the drive roll. The application of tension is caused by movement of said cam. The pressure roll further comprises a plurality of pressure rolls mounted on a pressure roll shaft and the drive roller comprises at least one drive roller mounted on a drive roll shaft.

According to a third embodiment, a pressure roll linkage for applying variable pressure to a pressure roll comprises a pivotable follower plate, the follower plate is engaged by a mover to cause pivotal movement of said follower plate, a pressure roller housing is adjacent the follower plate, the pressure roller housing has at least one pressure roller; a biasing member has a first portion and a second portion, the first portion is connected to the follower plate and the second portion is connected to the pressure roller housing; wherein actuation of the mover varies pressure applied by the pressure roller. The follower plate pivots in a first direction and the pressure roller housing pivots in a second opposite direction when loading the biasing member. The pressure roller moves toward and away from a drive roll when the mover is actuated and deactuated. The biasing member is a spring which is tensioned and untensioned as the mover is actuated and deactuated. The linkage is positioned in a printer feedpath. Alternatively, the linkage may be positioned in a scanner auto-document feeder feedpath. The mover may be an eccentric cam.

According to a fourth embodiment, a variable force pressure roll linkage comprises a media feedpath, a drive roller located along the media feedpath, a biasable idler roller rotatably disposed opposite and biased toward the drive roller and forming a nip therebetween for feeding media, and, a variable force means which decreases biasing force on the idler roller during media exit from the nip.

According to a fifth embodiment, a variable force pressure roll linkage comprises a media feedpath, a drive roller located along the media feedpath, an idler roller disposed opposite and biased toward the drive roller, a first linkage and a second linkage connected by a biasing member, the idler roller rotatably connected to the second linkage; and, motion means operably coupled to the first linkage for varying force on the idler roller during media feed.

The present invention allows for varying of force on a pressure roller when a media trailing edge passes a feed nip thereby inhibiting media jump and printing and scanning degradation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of an all-in-one device with printing component and a scanning component;

FIG. 2 is a perspective view of the all-in-one device of FIG. 1 with a cut-away section depicting the printing components;

FIG. 3 is a side view of a printing feedpath including an apparatus for varying pressure roll nip force;

FIG. 4 is a perspective view of the apparatus for varying pressure roll nip force;

FIG. 5 is a side view of the printing feed path and apparatus of FIG. 3 in a second position;

FIG. 6 is a perspective view of the apparatus in the second position shown in FIG. 5;

FIG. 7 is a perspective view of an alternative all-in-one device with a C-shaped printing feedpath;

FIG. 8 is a side view of the print feedpath of FIG. 7; and,

FIG. 9 is a side schematic view of a scanner auto-document feeder having an apparatus for varying pressure roll nip force.

DETAILED DESCRIPTION

It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.

In addition, it should be understood that embodiments of the invention include both hardware and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software. As such, it should be noted that a plurality of hardware and software-based devices, as well as a plurality of different structural components may be utilized to implement the invention. Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative mechanical configurations are possible.

The term image as used herein encompasses any printed or digital form of text, graphic, or combination thereof. The term output as used herein encompasses output from any printing device such as color and black-and-white copiers, color and black-and-white printers, and all-in-one devices that incorporate multiple functions such as scanning, copying, and printing capabilities in one device. Such printing devices may utilize ink jet, dot matrix, dye sublimation, laser, and any other suitable print formats. The term button as used herein means any component, whether a physical component or graphic user interface icon, that is engaged to initiate output.

Referring now in detail to the drawings, wherein like numerals indicate like elements throughout the several views, there are shown in FIGS. 1-9 various aspects of an apparatus for varying nip pressure in a media feedpath. The apparatus provides various functions including varying pressure roll force to decrease nip pressure and therefore substantially eliminate media jump. The apparatus may be utilized with printing components as well as ADF scanners.

Referring initially to FIG. 1, an all-in-one device 10 is shown having an ADF scanner portion 12 and a printer portion 20, depicted generally by the housing. The all-in-one device 10 is shown and described herein, however one of ordinary skill in the art will understand upon reading of the instant specification that the present invention may be utilized with a stand alone printer, copier, ADF scanner, or other device utilizing a media feed system. The peripheral device 10 further comprises a control panel 11 having a plurality of buttons for making selections. The control panel 11 may include a graphics display to provide a user with menus, choices or errors occurring with the system.

Still referring to FIG. 1, extending from the printer portion 20 are an input tray 22 at the rear of the device 10 and an exit tray 24 extending from the front of the device 10. A media feedpath 21 (FIG. 3) extends between the input tray 22 and output tray 24. The printer portion 20 may include various types of printing mechanisms including a laser printing mechanism or an ink-jet printing mechanism. For ease of description, the exemplary printer portion 20 is an inkjet printing device.

Referring now to FIG. 2, an interior cut-away perspective view of the all-in-one device 10 is depicted. With the interior shown, the printing portion 20 includes a carriage 26 having a position for placement of at least one print cartridge 28. FIG. 2 depicts two print cartridges 28 which may be, for instance, a color cartridge for photos and a black cartridge for text printing. As one skilled in the art will recognize, the color cartridge may include three inks, i.e., cyan, magenta and yellow inks. Alternatively, in lower cost machines, a single cartridge may be utilized wherein the three inks, i.e., cyan, magenta and yellow inks are simultaneously utilized to provide the black for text printing or for photo printing. During advancement media moves from the input tray 22 to the output tray 24 in a substantially L-shaped path along the media feedpath 21 beneath the carriage 26 and cartridges 28. As the media moves into a printing zone, the media moves in a Y-direction as depicted and the carriage 26 and the cartridges move in an X-direction which, is transverse to the movement of the media M.

Referring again to FIG. 1, the scanner portion 12 generally includes an ADF scanner 30, a scanner bed 17 and a lid 14 which is hingedly connected to the scanner bed 17. Beneath the lid 14 and within the scanner bed 17 may be a transparent platen for placement and support of target or original documents for manually scanning. Along a front edge of the lid 14 is a handle 15 for opening of the lid 14 and placement of the target document on the transparent platen (not shown). Adjacent the lid 14 is an exemplary duplexing ADF scanner 30 which automatically feeds and scans stacks of documents which are normally sized, e.g. letter, legal, or A4, and suited for automatic feeding. Above the lid 14 and adjacent an opening in the ADF scanner 30 is an ADF input tray 18 which supports a stack of target media or documents for feeding through the auto-document feeder 30. Beneath the input tray 18, the upper surface of the lid 14 also functions as an output tray 19 for receiving documents fed through the ADF scanner 30.

Beneath the ADF scanner 30 is an optical scanning unit having a plurality of parts which are not shown but generally described herein. The scanning unit may comprise a scanning motor and drive (not shown) which connects the scanning motor and a scanbar 280, shown generally in FIG. 9. The scanbar 280 is driven bi-directionally along a scanning axis extending in the direction of the longer dimension of a scanner bed. At least one guide bar may be disposed within the scanner bed 17 and may extend in the direction of the scanning axis to guide the scanning bar 280 along the scanning axis. The scanbar 280 moves along the at least one guide bar within the scanner bed 17 beneath the platen. The scanbar 280 has a length which extends in the shorter dimension of the scanning bed. Thus, the scanbar 280 extends across one dimension and moves in a perpendicular dimension to scan an entire surface area of the platen during flatbed scanning. Further, the scanbar 280 may be positioned beneath an ADF window for scanning documents fed through the ADF.

The scanbar 280 may include a lamp, an image sensor, and a mirror therein for obtaining a scanned image from a document. The image sensor may be an optical reduction type image sensor or a contact image sensor (CIS) as is known in the art. In either event, the image sensor then determines the image and sends data representing the image to onboard memory, a network drive, or a PC or server housing, a hard disk drive or an optical disk drive such as a CD-R, CD-RW, or DVD-R/RW. Alternatively, the original document may be scanned by the optical scanning component and a copy printed from the printer portion 20 in the case of a multi-function peripheral device 10. The scanbar 280 is generally either an optical reduction type using a combination of lens, mirror and a CCD (Charge Coupled Device) array or CIS array. The CCD array is a collection of tiny, light-sensitive diodes, which convert photons into electrons. These diodes are called photosites—the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site. The image of the document that is scanned using a light source such as a fluorescent bulb reaches the CCD array through a series of mirrors, filters and lenses. The exact configuration of these components will depend on the model of scanner. Some optical reduction scanners use a three pass scanning method. Each pass uses a different color filter (red, green or blue) between the lens and CCD array. After the three passes are completed, the scanner software assembles the three filtered images into a single full-color image. Most optical reduction scanners use the single pass method. The lens splits the image into three smaller versions of the original. Each smaller version passes through a color filter (either red, green or blue) onto a discrete section of the CCD array. The scanner software combines the data from the three parts of the CCD array into a single full-color image.

In general, for inexpensive flatbed scanners CIS arrays are used in the scanbar. CIS arrays replace the CCD array, mirrors, filters, lamp and lens with an array of red, green and blue light emitting diodes (LEDs) and a corresponding array of phototransistors. The image sensor array consisting of 600, 1200, 2400 or 4800 LEDs and phototransistors per inch (depending on resolution) spans the width of the scan area and is placed very close to the glass plate upon which rest the image to be scanned. Another version of the CIS uses a single set of red, green and blue LEDS in combination with light pipes to provide illumination of the material to be scanned. When the image is scanned, the LEDs combine to provide a white light source. The illuminated image is then captured by the row of sensors. CIS scanners are cheaper, lighter and thinner, but may not provide the same level of quality and resolution found in most optical reduction scanners. Color scanning is done by illuminating each color type of LED separately and then combining the three scans.

Referring now to FIGS. 3-4, exemplary internal components of a print feedpath 21 of the all-in-one device 10 are depicted in a side schematic view and perspective view, respectively. Media M is disposed in the input tray 22, which is the beginning of the feedpath 21 extending to the exit tray 24 where media M is collected after printing. A frame 52 is located within the housing of the all-in-one device 10 is depicted generally and extends vertically adjacent the variable pressure roll linkage 50. The frame 52 may include the printer frame or some other fixed structure within the all-in-one device 10 which is generally fixed relative to other moving parts. Extending through the frame 52 is a cam shaft 54. Operably connected to the cam shaft 54 is a cam 58 which either rotates with and/or rotates about the cam shaft 54. The cam 58 is generally round in shape but may take various geometric shapes which provides the function described further herein. The cam 58 is rotatably connected to the cam shaft 54 so that it rotates along a preselected eccentric profile or off center manner so that the rotation of the cam 58 about the pivot point 56 provides motion for linkage 50 and the pressure roll 44. Alternatively, some device may be substituted for the cam 58, such as a solenoid or other such mover which functions with the variable pressure roll linkage 50.

Adjacent the cam 58 is a first upper linkage 60 which functions as a follower and remains engaged to the cam 58. The first linkage 60 may comprise various shapes but is exemplarily depicted as rectangular with a first end 66 and a second end 68. The first linkage 60 is pivotally connected at a pivot point 62 either indirectly or directly to a fixed structure, such as the frame 52. The cam 58 engages the linkage 60 at contact point 64 and remains in contact during operation. As the cam 58 rotates, the first linkage or follower 60 moves from a normal position (shown in FIG. 3) wherein the pressure roll 44 is loaded to a second position where the pressure roll 44 is generally unloaded. The cam 58 may be rotated by various components including a motor and transmission such as belt drive or gear drive. Alternatively, the cam 58 may be driven by a gear drive and motor utilized for media advancing. It should be understood by one skilled in the art that various motion means may be used to cause movement and vary pressure on the pressure roller 44.

At the second end of the first linkage 60 is a biasing or elastic member 70 having a first end 72 and a second end 74. The biasing member 70 is depicted as a coil spring but one of ordinary skill in the art will recognize that various alternative biasing devices may be utilized to connect the first linkage 60 and a second linkage 80. The biasing member 70 is shown in its normal extended or tensioned position between the first linkage 60 and the second linkage 80. In the normal extended position, the pressure roll 44 is biased toward the feed roll 42 and contacts the feed roll 44 unless media M is moving there between. The cam 58 may circular as shown and positioned on cam shaft 54 so that the centerline of cam 58 is not coincident with the rotational centerline of cam shaft 54 as shown in FIG. 3. Alternatively, cam 58 may be oval or elliptical in shape and be mounted so that its centerline is coincident with the centerline of cam shaft 54. Either form of cam provides a preselected eccentric profile or path along which first linkage 60 travels as the cam 58 is rotated such that the pressure provided by biasing member 70 transitions from a predetermined maximum amount to a predetermined minimum amount. This can be accomplished by rotating the cam in a single direction or by reversing the direction of rotation of the cam. It should be realized that if the cam rotation is reversible that the configuration of the cam need not be circular or elliptical but may be semi-circular or semi-elliptical. The particular form and method of rotating the cam is left to the artisan.

The second linkage or pressure roll housing 80 is also pivotally connected to the frame 52 at pivot point 82. The second linkage 80 has a first end 84 and a second end 86 disposed on either side of the pivot point 82. The first end 84 is connected to the first linkage 60 by the biasing member 70. The second end of the second linkage 86 has at least one pressure roll 44 and according to one embodiment may have a plurality of pressure rolls 44 in contact with a feed roll 42. The contact between the feed roll 42 and the pressure roll 44 defines a nip 46 wherein media M is grasped for feeding to the printing zone beneath cartridge 28. The pressure rolls 44 are rotatably connected to the pressure roll housing 80 so as to rotate freely with the rotation of the feed roll 42 or media M passing between the pressure and feed rollers 44, 42. With the pressure rolls 42 forcing the media M into contact with the feed roll 42 as the feed roll turns, the media sheet M moves with the rotation of the feed roll 42 toward the exit system 36. The cam 58 is shown in contact with contact point 64 of the first linkage or follower 60. A mark “A” on the cam 58 is depicted at the contact point 64 for purpose of reference.

The exit system 36 comprises a driven exit roller 38 and an idler roller such as a star wheel 37. The star wheel design is used to minimize ink degradation during media feeding and is known to one skilled in the art. The drive or exit roller 37 directs media to the exit tray 24 through a feed nip defined between the rollers 37,38.

Referring now to FIGS. 5-6, the cam 58 has been rotated 180 degrees and the mark “A” is moved from its position in FIGS. 3-4. Accordingly, the follower 60 pivots about pivot 62 and follows the eccentric cam 58. Because of the shape of the cam 58, the follower 60 is positioned closer to the pivot point 56 defined by the cam shaft 54. The follower 60 pivots about pivot point 62 at a steeper angle so that the lower end 68 of the follower 60 moves downwardly and unloads the biasing member 70. By unloading the biasing member 70, the force directed through the biasing member and acting on the second linkage 80 is decreased or substantially removed such that the linkage 80 pivots about pivot point 82 and so that the second end 86 of the linkage 80 moves upward. As a result, the pressure roll 44 is no longer pressed as heavily against feed roll 42 and can move away from the feed roll 42.

Referring to FIGS. 1-6, in operation the linkage or variable force means 50 varies the force on the pressure or idler roller 44. First, media M is positioned in the input tray 22 for feeding through the feed path 21. The media M is advanced into the feed path 21 through the use of various components (not shown), for instance, an auto-compensating mechanism as known in the art. As the media M advances from the input tray 22 through the feed path 21 and to the nip 46, the at least one pressure roll 44 is in contact with the feed roll 42 forcing the media M to move toward the print zone defined under the cartridge 28. After moving through the print zone, the leading edge of media M is engaged by the exit system 36 which continues pulling the media through the print zone. As the media M continues to move through the feed nip 46 and through the print zone, the trailing edge of the media approaches the nip 46. Simultaneously, the cam 58 begins rotation from its position shown in FIG. 3 to its position shown in FIG. 5. During such rotation, the first linkage 60 pivots about its pivot point 62 toward the cam shaft 54 which in turn relieves tension on the biasing member 70. The contact point 64 of the first linkage 60 has moved toward the first end 66 of the first linkage 60 with the rotation of the cam 58 as the tension in the biasing member 70 is relieved, and the pressure roll 44 is moved upwardly from the feed roll 42 and media M such that a space is defined therebetween. As a result, when the trailing edge of media M passes through the nip 46, the media M is not urged toward the exit system 36 as with prior art devices. This design comprising a first linkage 60 and a spring connected second linkage 80 is advantageous because rotation of the cam 58 provides a gradual movement of the second linkage 80 and roller 44. Such gradual movement inhibits printing defects as opposed to a sudden linkage movement which can occur with the direct engagement of a cam and the second linkage or pressure roller housing 80. Thus, the present invention utilizes a variable force on the pressure roll 44 rather than a continuous force so that the media trailing edge is not urged forwardly along the feed path toward the print cartridge 28 and exit system 36. Further, the linkage system 50 allows for greater movement of the mover, such as the cam 58, resulting in only slight movement of the pressure roller 44.

Referring now to FIG. 7, an alternative embodiment of an all-in-one device 110 is depicted comprising a scanner 12 and a printer portion 120. The scanner portion 12 comprises an auto-document feed (ADF) scanner 30 and a flat bed scanner, generally depicted at 117. The ADF scanner 30 comprises an input tray 118 and an output tray 119, the device further comprises a scanner bed 117 and a lid 114 attached to the scanner bed 117. Upon opening of the lid 114, a platen (not shown) is revealed where documents, photos or drawings may be placed for flatbed scanning. The ADF scanner 30 is preferable for use in scanning stacks of documents and other such media sizes which are appropriately sized for such automatic scanning. The printing portion 120 comprises an input tray 122 and an exit or output tray 124 disposed above the input tray and thereby defining a C-shaped printing path, as opposed to the L-shaped path of the device shown in FIG. 1.

Referring now to FIG. 8, a side schematic view of an exemplary C-path printing portion 120 is depicted which may be utilized in the all-in-one device 110 shown in FIG. 7. The side view of the printing portion 120 has some detail removed for purpose of clarity. A plurality of media M is disposed on the input tray 122 at a lower portion of the printing portion feed mechanism. Generally, the media M is picked by a paper picking mechanism, such as an auto-compensating mechanism 130 and directed upwardly into the feed path 121. The feed path is substantially C-shaped and directs the leading edge of the media to the variable pressure roll linkage 150. The variable pressure roll linkage 150 extends from a fixed structure 152, such as a frame, and comprises a cam 158 which rotates about a cam shaft 154 to move a first linkage 160 that pivots about pivot point 162 and causes variable loading of a biasing member 170. By loading and unloading the biasing member 170 a second linkage 180 pivots at pivot point 182 causing application of force at the pressure roll 144 against the feed roll 142. As previously described, as the trailing edge of a media sheet approaches the nip 146 defined between the pressure roll 144 and the feed roll 142, the cam 158 is rotated about its pivot point 156 so as to untension the biasing member 170 and cause the pressure roll 144 to move away from the feed roll 142. With the pressure roll 144 not applying pressure to the media, the media jump which causes printing degradations is removed. As previously noted, the leading edge of the media is engaged by the exit system 136 before the pressure roll 144 completely disengages the media M so that the media is pulled through the print zone by the exit system 136. Thus, when the pressure roll 144 disengages from the feed roll 142, the media maintains its advancement through the printer feed path 121. This media disengagement point with the feed roll 142 can be sensed, using a flag or other means as is known in the art for position sensing, and the force on the pressure rolled can be increased either to the maximum amount of pressure available or some intermediate amount of pressure by rotating cam 158 prior to the arrival of the next sheet of media at the feed roller 142. Conversely, the pressure at nip 146 can be increased after arrival of the next sheet of media at feed roller 142 is sensed.

Referring now to FIG. 9, a side schematic view of the ADF scanner 30 is depicted which may be utilized in either all-in-one device 10, 110 (FIGS. 1 and 7) or in a standalone capacity. The ADF scanner 30 is depicted including various portions of the feedpath 221 as well. A pick system 233 is shown disposed above the input tray 18 for moving an uppermost media sheet from a media stack into the feedpath 221. The pick system 233 may comprise an auto-compensating mechanism, as known in the art, or may comprise alternate media picking components. Near the entrance portion of the feedpath 221 is a delivery system 230 which receives media moved by the pick or input system 233. The delivery system 230 comprises at least one delivery drive roller 232 and at least one delivery idler roller 234. A motor and gear train or other transmission (not shown) cause rotation of the delivery drive roller 232 for feeding the media M along feedpath 221. The delivery idler roller 234 includes at least one roller that rotates freely on an idler shaft 237. The at least one delivery idler roller 234 is biased toward the at least one delivery drive roller 232 by a biasing member (not shown), such as a leaf spring to form a nip 235 between the delivery drive roller 232 and the delivery idler roller 234. The delivery system 230 receives media M picked by the pick system 233 and feeds the media M through the feedpath 221 to a feed system 240.

The feed system 240 comprises a feed drive roller 242 and an opposed feed pressure roller 244. A motor and gear train or other transmission (not shown) cause rotation of the feed drive roller 242 for feeding the media M along feedpath 221. The feed pressure roller 244 is biased toward the feed drive roller 242 defining a nip 246 therebetween which receives media M from the delivery system 230 and directs the media M across a scanning station 280. The pressure roller 244 is biased toward the feed drive 242 by a variable force pressure roll linkage 250, as previously described. Accordingly, a rotatable cam 258 or motion device operably mounted on cam shaft 254 causes movement of a pivotable follower or first linkage 260 that pivots about pivot point 262 on frame 252 and which is connected to the pressure roller 264 via a biasing member 270 and second pivotable linkage 280 that pivots about pivot point 282 on frame 252. As the biasing member 270 is tensioned the pressure roller 244 engages the drive roller 242. When the biasing member 70 is unbiased, the pressure roller 244 moves away from the feed drive roller 242. Rotation of the cam 258 causes the increase or decrease in the amount of pressure exerted by the pressure roller 244 on the feed drive roller 242 at the nip 246.

Between the feed system 240 and the exit system 336 is a scanbar 300 including a representative scanning image sensor 302 schematically depicted as a series of mirror and a sensing element. As previously discussed, media M passing through the feedpath 221 is exposed to light in order to acquire image data of the image or text on the media. The variable force pressure roll linkage 250 is useful in the present embodiment because with a feed system having a biased pressure roller at a constant pressure media M can jump as the trailing edge of media M exits through the nip of such a feed system.

In operation, the pick system 233 directs media M from the media tray 18 into the feedpath 221. The media M reaches the delivery system 230 and is further directed to the feed system 240 through the feedpath 221. The pressure roller linkage 250 is disposed in the first position to cause engagement between pressure roller 244 and the feed drive roller 242. As the feed drive roller 242 causes advancement of the media M toward the image sensor 300 and associated scan area, the trailing edge of the media M approaches the feed system 240. Prior to the trailing edge of the media M reaching nip 246 defined between the rollers 242, 244, the linkage 250 is operated so as to vary pressure on the feed drive roller 262 by the pressure roller 264. At this point the linkage 250 is operated so that the pressure in the nip 246 is substantially reduced or is negligible. In other words, the moving device causes actuation of the first and second linkages 260, 280 as well as the biasing member 270.

With the various embodiments described herein after the trailing edge of the media M exits the nip, the variable pressure linkages 50, 150, and 250 can be operated such that the pressure exerted by the pressure rollers 44, 144 and 244 at nip is increased until the desire feeding pressure is reached. This can occur prior to the leading edge of the next sheet of media M reaching nip 46, 146, 246 or it may occur after the next sheet in already within the nip. For example, it may be advantageous with thicker media to have reduced pressure at nip possibly preventing damage to the edge of the media or allowing a reduction in the amount of force need to drive such media along the media feedpath.

The present invention allows for varying of force on a pressure roller when a media trailing edge passes a feed nip thereby inhibiting media jump and printing and scanning degradation.

The foregoing description of several methods and an embodiment of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto. 

1. An apparatus for varying nip pressure in a media feedpath including a feed roller and a pressure roller defining a feed nip therebetween, comprising: a rotatable cam having a preselected eccentric path when rotated; a first pivotable linkage pivotally engaging said rotatable cam; a second pivotable linkage; a biasing member operably interconnecting said first and second pivotal linkages for providing a biasing force on said pressure roller; and, said pressure roller rotatably connected to said second linkage opposite said biasing member; wherein rotation of said cam varies the biasing force provided by said biasing member on said pressure roller.
 2. The apparatus of claim 1 wherein said cam has an eccentric shape.
 3. The apparatus of claim 2 further comprising a rotatable shaft operably connected to said cam.
 4. The apparatus of claim 1 wherein said first linkage pivots about a first linkage pivot point as said cam rotates.
 5. The apparatus of claim 1 wherein rotation of said cam the loads and unloads said biasing member connected to said first linkage and said second linkage as said cam is rotated.
 6. The apparatus of claim 5 wherein said pressure roller exerts greater force on said feed roll as said biasing member is loaded and exerts lesser force on said feed roll as said biasing member is unloaded.
 7. The apparatus of claim 1, wherein said pressure roller comprises a plurality of pressure rollers.
 8. A variable pressure roll linkage for media feedpath, comprising: an elastic member; a first linkage; a feed drive roller and a pressure roller defining a nip therebetween; a second linkage with said pressure roller operably connected to said second linkage with said first linkage connected to said second linkage by said elastic member; and, a cam moveable about a preselected profile engaging said first linkage wherein movement of said cam loads and unloads said elastic member and causes translation of said pressure roller at said nip.
 9. The variable pressure roll linkage of claim 8, wherein said pressure roller is translatable toward and away from said feed drive roller.
 10. The variable pressure roll linkage of claim 8 wherein rotation of said cam pivots said first linkage.
 11. The variable pressure roll linkage of claim 8, said elastic member further comprising a spring.
 12. The variable pressure roll linkage of claim 8 wherein application of tension to said elastic member increases force of said pressure roll toward said drive roll.
 13. The variable pressure roll linkage of claim 12, said application of tension is caused by movement of said cam.
 14. The variable pressure roll linkage of claim 8, said pressure roll further comprising a plurality of pressure rolls mounted on a pressure roll shaft and said drive roller comprising at least one drive roller mounted on a drive roll shaft.
 15. A pressure roll linkage for applying variable pressure to a pressure roll, comprising: a pivotable follower plate; said follower plate engaged by a mover to cause pivotal movement of said follower plate; a pressure roller housing adjacent said follower plate, said pressure roller housing having at least one pressure roller; and, a biasing member having a first portion and a second portion, said first portion connected to said follower plate and said second portion connected to said pressure roller housing; wherein actuation of said mover varies pressure applied by said pressure roller.
 16. The pressure roll linkage of claim 15 wherein said follower plate pivots in a first direction and said pressure roller housing pivots in a second opposite direction when loading said biasing member.
 17. The pressure roll linkage of claim 15, said pressure roller moving toward and away from a drive roll when said mover is actuated and deactuated.
 18. The pressure roll linkage of claim 15, said biasing member being a spring which is tensioned and untensioned as said mover is actuated and deactuated.
 19. The pressure roll linkage of claim 15, said linkage positioned in a printer feedpath.
 20. The pressure roll linkage of claim 15, said linkage positioned in a scanner auto-document feeder feedpath.
 21. The pressure roll linkage of claim 15 said mover being an eccentric cam.
 22. A variable force pressure roll linkage, comprising: a media feedpath; a drive roller located along said media feedpath; a biasable idler roller rotatably disposed opposite and biased toward said drive roller and forming a nip therebetween for feeding media; and, a variable force means which decreases biasing force on said idler roller during media exit from said nip.
 23. A variable force pressure roll linkage, comprising: a media feedpath; a drive roller located along said media feedpath; an idler roller disposed opposite and biased toward said drive roller; a first linkage and a second linkage connected by a biasing member; said idler roller rotatably connected to said second linkage; and, motion means operably coupled to said first linkage for varying force on said idler roller during media feed. 